It is intended to provide an administration instrument for medical use whereby a drug solution can be safely injected at a high reliability. Using this instrument, for example, a needle can be prevented from sticking deeper into the skin due to the force applied for pressing an injection button and, at the same time, maintained without shaking to ensure stable administration, thereby relieving physical and mental pains of a patient. Owing to the structure wherein an injection button (3) is pressed from an angle not parallel to the direction along which a needle (4) sticks into the skin, the needle can be prevented from sticking deeper into the skin than the level at the beginning due to the force applied for pressing the injection button, thereby ensuring stable administration.